Biological and cytological-morphological assessment of tuberculous pleural effusions

Tuberculosis (TB) came back in the top of causes for infectious disease-related deaths and its pleural involvement is still in the top two extrapulmonary sites. The authors continued their studies on TB pleural effusions (Pl-Effs) with the assessment of biological and cytological variable of pleural fluid (PF), introducing in the investigation algorithm and testing a new tool, the computer-assisted evaluation of cell populations on PF smears.

A series of 85 patients with TB pleurisy (PLTB) were selected from a larger group of 322 patients with different types of Pl-Effs. The algorithm of investigation included. clinical variables, biological assays of PF, gross aspects including imagistic variables and PF cytology on May-Grünwald-Giemsa (MGG)-stained smears. All the data obtained were entered into and processed using Microsoft Excel module of the 2019 Microsoft Office Professional software along with the 2014 XLSTAT add-in program for MS Excel. The PF cellularity was assessed qualitatively by a cytologist and quantitatively with in-house software. Continuous variables were compared using Pearson's correlation test, while categorical variables were compared using χ² (chi-squared) test.

Our analysis showed that patients were usually males, aged between 25 and 44 years with Pl-Eff discovered at clinical imagistic examination, almost always one-sided and free in the pleural cavity. Its extension was either moderate or reduced. The PF had a serous citrine appearance in most of the cases, and biological characteristics pleaded for an exudate [high levels of proteins and lactate dehydrogenase (LDH)], with elevated adenosine deaminase (ADA) values and rich in lymphocytes (Ly). The attempt to identify the pathogen in PF was not of much help. Apart from Ly, neutrophils [polymorphonuclear neutrophils (PMNs)] were a rare presence and their amount had only a trend of direct correlation with Ly. The same situation was encountered in the case of mesothelial cells (MCs). The comparison between the qualitative and the quantitative, computer-assisted evaluations of cytological smears showed that the results of the two methods overlapped in less than one third of the cases, although the sensitivity and specificity values as well as the two calculated predictive values of the qualitative method were encouraging.

The assessment of biological variables and cell populations of the PF are basic tools in the diagnosis of pleural TB. The assessment of PF cell population could be improved by the use of computer-assisted quantitative analysis of the PF smears, which is simple to design, easy to introduce and handle and reliable.